The present invention relates to a sound source searching device for searching an objective sound source out of a plurality of sound sources, and particularly to a sound source searching device employing an intensity probe.
In order to reduce noise produced in a large number of sound source of an internal combustion engine or the like, it is effective to search one sound source of which the sound pressure level is the maximum and prevent the sound source from producing noise.
For searching the above described sound source precisely, the detector having a sharp directivity against sound must be employed. Recently, the intensity probe has been noted as the above described detector.
The intensity probe (hereinafter, will be called "probe") is provided with two omnidirectional microphones 11a, 11b.
By making a frequency analysis of the sound pressure signals obtained by the microphones 11a, 11b, combining spectrums of the above sound pressure signals into a cross spectrum and calculating acoustic intensity (hereinafter, will be called "intensity") from the imaginary part of the cross spectrum, the directional characteristics as shown in FIG. 1 is obtained.
Namely, when the sound source approaches the plane including O.sub.I, Oc, O.sub.II, the intensity rapidly decreases.
In order to search an objective sound source, at first, by moving the probe on the first plane, the first direction in which the absolute value of intensity is the minimum is searched, then by moving the probe on the second plane including the above horizontal direction, which is perpendicular to the first plane, the second direction in which the absolute value of intensity is the minimum is searched, as the direction of sound source.
Conventionally, the above search has been performed by controlling the probe by hand, so it is difficult to search the sound source precisely even by use of great effort and a long period of time.